The present invention relates to materials having a substantial elemental sulfur matrix.
U.S. Pat. Nos. 5,935,313, 4,475,953, 4,290,816, 4,387,167 and 4,058,500 disclose certain sulfur compositions and their methods of formation. There is a need for a sulfur composition with improved compressive strength and/or a foamed sulfur structural or agricultural use product.
The present invention are methods for and products having an elemental sulfur matrix. The matrix is formed by using at least a minimum amount of shear force on molten elemental sulfur, in either a relatively pure or less pure form, where the molten sulfur is combined with materials causing nucleation, coalescence, colloidallization, and/or pore formation.
The present invention forms material with improved compressive and tensile strength, durability, elasticity, flammability, thermal conductivity, thermal expansion, adhesivity, permeability, radioactive attenuation, chemical and toxic material resistance and/or non toxic foaming.
Pore formation is the result of injecting gases or vaporizable liquids as materials combined with the molten sulfur.
The nucleating material comprises virtually any material solid at the processing temperature that is sufficiently small enough to obtain the objects of the invention or is broken into such small pieces that the objects are obtained. The coalescing material is a liquid or meltable solid fed into the molten sulfur while under the shear force. Gases or vaporizing material are introduced at the point of shear stress to mix with molten sulfur so that relatively small bubbles are formed, producing a lightweight product with great structural strength.
The present invention is a method of changing the previously known crystalline mineral structure of meltable materials into a solid or porous amorphous matrix, more particularly for forming new, durable structural materials or a porous matrix capable of releasing fertilizer nutrients in contact with biochemical environment in soils.
The present invention is also a method of using a substantial proportion of unprocessed crude or recovered waste sulfur or sulfur impregnated rock that can be combined with other materials to form the above novel matrices. The sulfur matrix can be formed with micronized wollastonite, limestones, silica and silicates, urea, clays, borax salts, phosphates, asphalts, bitumens, tars, resins, rubbers, coals, lignites, peats, caoutchouc, paraffins, iso-paraffins, vinyls, poly-uretans, micronized oxides of lead, iron, barite, fly ash, furnace slag, ceramics of various kind, mineral or glass or carbon or steel or asbestos or combination of the said fibers, wooden chips and sawdust, straws, paper pulp.
The term xe2x80x9ccrude sulfurxe2x80x9d refers to unprocessed or unrefined sulfur containing more than 25% of elemental sulfur per weight, including calcium carbonate in natural sulfur ore body, sulfur impregnated volcanogenic silicates, sulfur from fumarols, non-purified sulfur from oil gas and metals purification processes, waste sulfur from vulcanization processes, and other such less pure sulfur forms. Pure or solid sulfur refers to crystalline or micro-crystalline sulfur as purified apart from other components or as the elemental sulfur portion of the less pure forms.
Solid sulfur has very low heat transfer coefficient under very large temperature gradients and is nonconductive, unless combined with conductive carbon. However, its use as a structural material and as a chemical release matrix are virtually unknown in commercial practice because of solid sulfur""s the lack of structural integrity or the relatively high cost or complexity of the alternatives. Solid, crystalline sulfur, while rigid, is quite brittle and non-uniform in crystalline structure.
The invention product sulfur matrix or amorphous crystal structure is formed upon exposure to shear stress in the presence of one or more of the matrix forming materials and subsequent solidification. Re-melting and resolidification appear not to affect matrix re-formation to give substantially the same product properties. The relatively intense mixing of the invention distributes the matrix forming materials substantially uniformly throughout the melt such distribution is advantageously maintained regardless of re-melting.
The process of the present invention is the substantially even distribution of nucleating material and/or coalescing material within a molten sulfur so that solidification creates a matrix which has structural integrity for structural members or chemical and/or moisture release of desirable nutrients, such as are used in agriculture and in one preferred embodiment as fertilizer.
The present invention comprises using mineral, metal, polymer, elemental, fiber or any such particles that do not melt at processing temperatures as nucleating materials. Nucleating materials are preferably about 100 microns or less in size and comprise such matter as wollastonite, limestones, silica and silicates, clays, borax salts, phosphates, humic acid, coals, lignites, peats, oxides of lead, iron, barite, fly ash, furnace slag, ceramics of various kind, mineral or glass or carbon or steel or asbestos or combination of the said fibers, wooden chips and sawdust, straws, paper pulp, chromium salts, depleted uranium. While one embodiment comprises using particles at the desired size for mixture with the molten sulfur, another embodiment permits particles of substantial size that are ground to a desired size in the processing equipment generating the shear stress for mixing the nucleating materials.
Coalescing materials substantially enhance the nucleation effect of nucleation material mixing in the molten sulfur. The following are preferable coalescing materials in a liquid or meltable form, i.e., meltable at processing conditions: urea, asphalts, bitumens, tars, resins, rubbers, caoutchouc, paraffins, iso-paraffins, vinyls, polyurethanes. Although adequate nucleation is achieved without the coalescing material for the objects of the present invention, coalescing materials can reduce the processing time required for obtaining the desired final product properties.